Will tropical coral reefs be the first ecosystem to be eliminated by climate change?

Monday, May 07, 2007

An impoverished place

A World Without Corals? by Richard Stone (News Focus, Science, 4 May) covers most of the bases on reporting of this issue, with an update on what some are saying the effects of acidification, and who is listening (analysis of events to date last year has been previously reported in several places including here and here):

IPCC scenarios of global emissions and ocean circulation indicate that by midcentury, atmospheric CO2 levels could reach more than 500 parts per million, and near the end of the century they could be above 800 ppm. The latter figure would decrease surface water pH by roughly 0.4 units, slashing carbonate ion concentration by half, paleocoral expert C. Mark Eakin, coordinator of NOAA's Coral Reef Watch, testified last month at a hearing in the U.S. House of Representatives. Ocean pH would be "lower than it has been for more than 20 million years," he said. And that does not factor in possible acidification from carbon-sequestration schemes now being considered.

Some coral species facing their acid test may become shape shifters to avoid extinction. New findings indicate that corals can survive acidic conditions in a sea anemone-like form and resume skeleton-building when returned to normal marine conditions (Science, 30 March, p. 1811). However, by pH 7.9, says [Ken] Caldeira [of the Carnegie Institution of Washington in Palo Alto, California], "there would be a good chance reefs would be gone."

The potential for an acid-induced coral cataclysm has cast a pall on the tight-knit community of reef specialists. "The reality of coral reefs is very dark, and it is very easy for people to judge coral reef scientists as pessimists," says [Camilo] Mora [of Dalhousie University in Halifax, Canada]. "We're becoming alarmist," adds [Alan] Strong [senior consultant to NOAA's Coral Reef Watch] --for good reason, he insists. "How are reefs going to handle acidification? It's not like sewage or runoff, where you may be able to just turn off the spigot."

Among other key assertions as reported: 1) it [may be] "too early to make really definitive doom-and-gloom statements" (Pandolfi); and 2) "the threat of millions of people losing their livelihoods must be factored into policy planning" (Hoegh-Guldberg):

[John] Pandolfi [of the University of Queensland in Brisbane, Australia], however, argues that it's "too early to make really definitive doom-and-gloom statements."

No one disputes that urgent action on greenhouse gas emissions is essential. "We could still have vibrant reefs in 50 years time," ...says [Terence Hughes, director of the Australian Research Council's Centre of Excellence for Coral Reef Studies at James Cook University in Townsville, Australia]. But these will not be the reefs we know today. "They will be dominated by a different suite of species," says Hughes, who notes that the shakedown is already under way.

More likely, steps to rein in emissions will be too little, too late--and the world will have to brace for the loss of reefs. In Southeast Asia, says [Ove] Hoegh-Guldberg [director of the Centre for Marine Studies at the University of Queensland in St. Lucia, Australia], the threat of millions of people losing their livelihoods must be factored into policy planning. Coastal dwellings throughout the tropics will have to be strengthened against higher waves. Then there is the intangible, aesthetic deprivation if coral reefs wither and wink out. "Without their sheer beauty," Hughes says, "the world would be an impoverished place."

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"Mike", the world's first hydrogen bomb, vaporised Elugelap island and other parts of the Enewetak atoll on 1 November 1952. In the half century or so since then humans have destroyed around a quarter - some say a half - of all tropical coral reefs, which are one the world's richest and oldest ecosystems and provide vital benefits in over 100 countries. Will the rest be gone within another fifty years - or less? So what?

Please note that this blog is now pretty much 'on hold', with only occasional updates since January 2008. For notes on the Anthropocene extinction and what comes next see The Book of Barely Imagined Beings.